diff --git a/packages/koishi-core/src/database.ts b/packages/koishi-core/src/database.ts
index 3a6c67c8dd..c72e163380 100644
--- a/packages/koishi-core/src/database.ts
+++ b/packages/koishi-core/src/database.ts
@@ -23,7 +23,7 @@ export namespace User {
 
   export type Field = keyof User
   export const fields: Field[] = []
-  export type Observed<K extends Field = Field> = utils.Observed<Pick<User, K>>
+  export type Observed<K extends Field = Field> = utils.Observed<Pick<User, K>, Promise<void>>
   type Getter = (id: number, authority: number) => Partial<User>
   const getters: Getter[] = []
 
@@ -94,13 +94,13 @@ export interface Database {
   getUser<K extends User.Field>(userId: number, defaultAuthority?: number, fields?: readonly K[]): Promise<Pick<User, K | 'id'>>
   getUsers<K extends User.Field>(fields?: readonly K[]): Promise<Pick<User, K>[]>
   getUsers<K extends User.Field>(ids: readonly number[], fields?: readonly K[]): Promise<Pick<User, K>[]>
-  setUser(userId: number, data: Partial<User>): Promise<any>
+  setUser(userId: number, data: Partial<User>): Promise<void>
 
   getGroup<K extends Group.Field>(groupId: number, fields?: readonly K[]): Promise<Pick<Group, K | 'id'>>
   getGroup<K extends Group.Field>(groupId: number, selfId?: number, fields?: readonly K[]): Promise<Pick<Group, K | 'id'>>
   getAllGroups<K extends Group.Field>(assignees?: readonly number[]): Promise<Pick<Group, K>[]>
   getAllGroups<K extends Group.Field>(fields?: readonly K[], assignees?: readonly number[]): Promise<Pick<Group, K>[]>
-  setGroup(groupId: number, data: Partial<Group>): Promise<any>
+  setGroup(groupId: number, data: Partial<Group>): Promise<void>
 }
 
 type DatabaseExtensionMethods<I> = {
diff --git a/packages/koishi-core/src/session.ts b/packages/koishi-core/src/session.ts
index 669ff78d11..b496d9f860 100644
--- a/packages/koishi-core/src/session.ts
+++ b/packages/koishi-core/src/session.ts
@@ -200,7 +200,7 @@ export class Session<U extends User.Field = never, G extends Group.Field = never
 
     // 确保匿名消息不会写回数据库
     if (this.anonymous) {
-      const user = observe(User.create(userId, defaultAuthority))
+      const user = observe(User.create(userId, defaultAuthority), () => Promise.resolve())
       return this.$user = user
     }
 
diff --git a/packages/koishi-utils/src/observe.ts b/packages/koishi-utils/src/observe.ts
index a2fc74592c..14b2e5e88c 100644
--- a/packages/koishi-utils/src/observe.ts
+++ b/packages/koishi-utils/src/observe.ts
@@ -134,7 +134,7 @@ export function observe<T extends object, R>(target: T, ...args: [(string | numb
 
   const observer = observeObject(target, label, null) as Observed<T>
 
-  defineProperty(observer, '_update', function (this: Observed<T>) {
+  defineProperty(observer, '_update', function _update(this: Observed<T>) {
     const diff = { ...this._diff }
     const fields = Object.keys(diff)
     if (fields.length) {
@@ -146,7 +146,7 @@ export function observe<T extends object, R>(target: T, ...args: [(string | numb
     }
   })
 
-  defineProperty(observer, '_merge', function (this: Observed<T>, value: Partial<T>) {
+  defineProperty(observer, '_merge', function _merge(this: Observed<T>, value: Partial<T>) {
     for (const key in value) {
       if (key in this._diff) {
         throw new Error(`unresolved diff key "${key}"`)